(670b) The Thermal Decompositions of Benzyl and o-Xylyl Radicals

The thermal decompositions of benzyl- (C₆H₅CH₂), benzyl α,ά-d₂- (C₆H₅CD₂), and o-xylyl-radicals (o-CH₃C₆H₄CH₂) have been studied at high temperatures with the reflected shock tube technique using H- and D-atom ARAS. The experiments were performed at high-T (1437-1801 K) at nominal pressures ≈ 0.3-1.3 atm.

Using the ultra-sensitive H- and D-atom ARAS technique, the present experiments reveal that there are three channels that contribute to benzyl decomposition: H-atom removal from the ring, H/D-atom removal from the side-chain, and a non-atom producing process (postulated to be cyclopentadienyl + acetylene). The experimental data was used to obtain rate constants for the three channels and also for total benzyl decomposition.

              We then initiated experimental studies on o-xylylbromide (o-CH₃C₆H₄CH₂Br) decomposition. Br-ARAS experiments used with the shock tube confirm that at high-T (>1200 K) o-xylyl radicals (o-CH₃C₆H₄CH₂) are generated instantaneously. The high sensitivity H-atom ARAS detection technique has been subsequently used to obtain quantitative measurements of the H-atom yields, and rate coefficients, for o-xylyl decomposition. These H-ARAS experiments span a T-range, 1267-1597 K, and pressure range, 0.3-1.0 atm. The results from these studies and comparisons to earlier studies are discussed.

              This work was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences, under Contract No. DE-AC02-06CH11357.